Delay Simulation (DELAYSIM)

DELAYSIM is a unique model originally developed for Massport to evaluate the original Preferential Runway Advisory System (PRAS) at Logan.  The model simulates how air traffic controllers might use the airport's runways based on specified demand characteristics and actual weather observations. It predicts hour-by- hour runway utilization, and estimates the associated aircraft delays.

DELAYSIM operates by sequencing through hourly weather observations and simulating the controllers' selection of runway for each hour. It averages the results to produce annual operating statistics. For each hour, the runway selection is a three-step process. DELAYSIM first identifies from all possible runway configurations those which are available based on the wind and visibility conditions. Second, the model identifies which (if any) of the available configurations has sufficient operational capacity to meet the demand in the current hour. If none of the configurations has sufficient capacity, the available configuration with the highest capacity is chosen. Third, if more than one configuration has enough capacity DELAYSIM selects the configuration based on the specified runway selection algorithm, taking into account controller workload for runway changes.   For analysis at Logan, DELAYSIM has been set up to simulate selection according to the Enhanced Preferential Runway Advisory System (ENPRAS) noise goals.  The model also has the capability of selecting the available configuration with the maximum capacity in each hour, which normally would represent the controllers' unconstrained preference.  Other runway selection algorithms have been created as needed.  For example, FTA created selection algorithms to reflect the Long-Term Operating Plan (LTOP) at Sydney Kingsford-Smith Airport and the runway selection preferences at Schiphol Airport in Amsterdam.

Once DELAYSIM selects a runway configuration, it calculates delays by comparing the saturation capacity of that configuration with the projected hourly demand using a queuing theory model (FTA's analytical DELAYS model). DELAYSIM captures all delays in its statistics, not just those operations delayed by more than 15 minutes (although those delays are identified). In addition, DELAYSIM assumes that all scheduled demand will eventually be handled. In other words, DELAYSIM does not cancel operations, it simply delays them until they can be served.  Stated another way, DELAYSIM includes the impacts of cancelled flights by estimating the additional delays that such flights would experience if they were to be completed.

In addition to producing detailed delay statistics, DELAYSIM generates configuration and runway use statistics by month, time-of-day, and day-of-week.  The model has also been used to annualize the results of other models which are not capable of long-term, dynamic analysis.  For example, in the Logan Airside Improvements EIS/EIR Project, DELAYSIM was used to annualize the results of individual Airport Machine analyses to generate annualized taxiway delay statistics.  The model has also been used to generate annualized inputs for environmental models such as the FAA's Integrated Noise Model (INM) and FTA's own Ground Noise Propagation Model (GNPM). 

DELAYSIM has most recently been used in studies at Boston Logan International Airport, Schiphol Airport, and Sydney Airport. At Logan, DELAYSIM was used to annualize the capacity analysis and evaluate the relative advantages of numerous airfield improvements. It also provided detailed output statistics used in taxiway, air quality, and noise impact modeling. In Sydney, DELAYSIM was used for two projects. First, it was used to assess the validity of the Long Term Operating Plan in terms of increases in annual capacity and modified runway use goals. In a second study, it was used to determine the potential impacts of the reinstatement of a southbound bias for all operations. At Schiphol, DELAYSIM was used to test potential methods to enhance the noise-capacity of the airport, including installation of an automated Preferential Runway Advisory System, changes in crosswind limits, and modifications to the current Preferential Runway System.


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